Dissertation Research: Phylogeny of Aplacophora and Polyplacophora and Evolution of Molluscan Calcareous Hard Parts

论文研究：无壳纲、多壁纲的系统发育及软体动物钙质硬质部分的演化

• 批准号: 0073312
• 负责人: Andrew Knoll
• 金额: $ 1万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2002-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0073312&HistoricalAwards=false
• 关键词: Dissertation; Research; Phylogeny; Aplacophora; Polyplacophora

0073312Knoll and OkusuGraduate student Akiko Okusu, under the direction of Dr. Andrew Knoll, Harvard University, is studying the phylogenetic relationships and the evolution of calcareous hard parts of aplacophoran and polyplacophoran molluscs using integrated data from DNA sequences, morphology, and embryology. Aplacophorans are worm-like deep-sea molluscs that have no shells but are covered by spicules made of the calcium carbonate mineral aragonite. Polyplacophorans (chitons) are flat elongate molluscs with eight dorsal shell-plates imbricated within a spicule-embedded mantle girdle. It has been postulated that aplacophorans are closely related to polyplacophorans, that the two groups represent the most basal groups of molluscs (based on their relatively simple features), and that their aragonite spicules reflect a more "primitive" type of calcium carbonate deposition than that found in other molluscs. However, the evolutionary relationships of the Aplacophora and the Polyplacophora are unresolved. The lack of a well-supported phylogeny calls into question hypotheses of evolutionary changes in molluscan form and mineral deposition. Molecular sequence data from highly conserved nuclear coding genes, EF1-alpha and POL-II, will be used to construct a phylogenetic framework for 40 taxa including representative species from major molluscan classes and outgroup species from the Sipuncula and Annelida. Spicule development and morphology in these groups will be analyzed within the phylogenetic framework in order to assess homology and pattern of evolutionary change. The results will have a major impact on our understanding of the origin and evolution of molluscs.

0073312Knoll 和 Okusu 研究生 Akiko Okusu 在哈佛大学 Andrew Knoll 博士的指导下，正在利用 DNA 序列、形态学和胚胎学的综合数据研究无板纲和多板纲软体动物的系统发育关系和钙质坚硬部分的进化。 无壳虫是蠕虫状的深海软体动物，没有壳，但覆盖着由碳酸钙矿物文石制成的针状物。 多板类（石鳖）是扁平细长的软体动物，有八块背壳板，叠瓦状排列在嵌有针状体的地幔带内。 据推测，无板纲动物与多板纲动物密切相关，这两个类群代表了软体动物的最基本类群（基于它们相对简单的特征），并且它们的文石针反映了比其他软体动物中发现的更“原始”类型的碳酸钙沉积。 然而，无板纲和多板纲的进化关系尚未解决。 缺乏得到充分支持的系统发育对软体动物形态和矿物沉积的进化变化的假设提出了质疑。 来自高度保守的核编码基因 EF1-α 和 POL-II 的分子序列数据将用于构建 40 个类群的系统发育框架，包括主要软体动物纲的代表性物种以及来自 Sipuncula 和 Annelida 的外类群物种。 将在系统发育框架内分析这些群体的针状发育和形态，以评估进化变化的同源性和模式。 研究结果将对我们对软体动物起源和进化的理解产生重大影响。